(1) Field of the Invention
This invention relates to an expansion valve, and more particularly to a block-type expansion valve which is employed as an expansion device in a rear-side part of the system of a so-called dual air conditioner for an automotive vehicle, which uses an orifice tube in a front-side part thereof.
(2) Description of the Related Art
Conventionally, as the system of the automotive dual air conditioner, there are known one which uses an orifice tube as a front-side expansion device, and one which uses an expansion valve as the same. Both of the systems use an expansion valve as a rear-side expansion device.
In the system which uses an orifice tube as the front-side expansion device, refrigerant compressed by a compressor is condensed by a condenser, and liquid refrigerant formed by complete condensation by the condenser is expanded in the orifice tube, evaporated by an evaporator, and caused to undergo gas/liquid separation by an accumulator. Gaseous refrigerant obtained by the separation is returned to the compressor.
On the other hand, in the system which uses an expansion valve as the front-side expansion device, refrigerant compressed by a compressor is condensed by a condenser, the condensed refrigerant is caused to undergo gas/liquid separation by a receiver/dryer, and liquid refrigerant obtained by the gas/liquid separation is expanded by the expansion valve, and completely evaporated by an evaporator, followed by returning to the compressor.
In general, the receiver/dryer not only separates gaseous refrigerant from liquid refrigerant and removes moisture but also clears foreign matter from the refrigerant circulating through the system with a strainer incorporated therein. Therefore, the refrigerant having passed through the receiver/dryer is sent into the front-side expansion valve in a state cleared of foreign matter. At this time, liquid refrigerant cleared of foreign matter by the receiver/dryer is also supplied to the rear-side expansion valve.
On the other hand, in the system which uses the orifice tube as the front-side expansion device, the liquid refrigerant delivered from the condenser is directly supplied to the front-side orifice tube and the rear-side expansion valve. Since the orifice tube is configured to incorporate the strainer as an integral part thereof, foreign matter in the refrigerant is removed on the inlet side of the orifice tube. However, for the rear-side expansion valve, since the refrigerant containing foreign matter is directly supplied thereto, a strainer is usually arranged in a pipe on the upstream side of the valve.
To incorporate the strainer in the pipe, the pipe needs being formed into a specific shape and increased man-hours are necessary for the assembly work, resulting in an increase in manufacturing costs. On the other hand, some of the conventional expansion valves contain a strainer and make it unnecessary to incorporate the strainer in the pipe.
The above strainer-containing expansion valve is called a joint connection-type or angle-type expansion valve, which includes connecting portions for connecting thereto a pipe extending from a condenser and a pipe leading to an evaporator. According to this type of valve, only the connecting portions can be lengthened with ease, and therefore the strainer can be inserted into an inlet-side connecting portion, by lengthening the same.
However, when the so-called box-type or block-type expansion valve is used as the rear-side expansion valve, it is necessary to incorporate a strainer in a pipe on the upstream side of the valve. More specifically, in the block-type expansion valve, the pipe is inserted to an intermediate portion of an inlet-side port, and there is no space for mounting the strainer in the port. Therefore, if the strainer is desired to be attached to the inlet-side port, it is necessary to extend an end of the body on a high-pressure refrigerant inlet side to make a hole of the port deep enough to mount the strainer at an inner portion of the hole. This increase in length and size of the body only for arranging the strainer therein results in an increase in the material cost and working cost of the body besides an additional cost of the strainer, which further increase the manufacturing costs of the expansion valve. To avoid such an disadvantage, it is necessary to incorporate the strainer in the pipe separately from the valve.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a low-cost block-type expansion valve containing a strainer.
To solve the above problem, the present invention provides an expansion valve of a block type including a power element for sensing a temperature and pressure of refrigerant delivered from an evaporator, and a valve portion containing a valve element in a block-shaped body thereof, characterized by comprising a hollow cylindrical strainer which is mounted in a fluid passage having said valve element arranged therein, in a manner surrounding said valve element.
According to this expansion valve, the strainer is configured to be mounted in a space of a refrigerant passage having the valve element arranged therein. Since the refrigerant passage is an existing one, it is possible to maintain the present costs of parts except for the cost of the strainer.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.